Gasketing materials are well known in the art and they play an important role in all facets of everyday life. A gasket is a device or medium used to create and maintain a barrier against the transfer of fluids across separable surfaces of a mechanical assembly that do not move relative to each other. Many types of gasket materials are presently in use. For example, asbestos-rubber, cellulose-rubber, cork composition, cork-rubber and rubber gaskets are all found in various phases of industry.
One of the most common types of gasketing is cork-rubber gasketing. Cork is a highly compressible material which lends itself to a wide variety of gasketing applications; nevertheless, it suffers from certain defects. For example, cork is porous and tends to swell when exposed to fuel and other petroleum-based products. Another problem related to the use of cork is that it is a natural material which is in finite supply. In recent years, the cost of cork has increased dramatically and this cost increase has led to widespread industry attempts to find replacement materials which are effective, yet which are lower in cost.
A filler material which has received increasing attention because of its low cost and availability is rice hulls, a by-product of rice refining. The individual rice hulls are light-weight fiberous materials which primarily contain cellulose, but which also comprise about 25% inorganic materials, much of which is silica.
Rice hulls have been used in animal feeds, in agriculture, as fuels, and as raw materials for the production of carbon particles, organic and inorganic chemicals, abrasives and refractory materials. In addition, they have been used as fillers for cements, building boards and the like. Nevertheless, they have not been used as cork substitutes in gasketing materials.
Despite widespread attempts to utilize rice hulls, the results have not been entirely satisfactory. The art contains reports that rice hulls require pretreatment with coupling and/or wetting agents in order to make them suitable for use as fillers. Alternative treatments have included the partial or complete incineration of the hulls to provide ash which has been used as a filler. Nevertheless, it has been found that such modifications increase the cost of the filler and often do not significantly improve its characteristics.
Accordingly, one objective of the present invention is to provide rice hull compositions wherein the rice hulls serve as replacements for conventional fillers.
Another objective of the present invention is to provide low-cost gasketing materials which exhibit superior performance characteristics.
Yet another objective of the present invention is to provide gasketing materials which are adaptable to conform to flange contours, thereby providing superior seals.
Still yet another objective of the present invention is to provide improved gasketing materials which will be resistant to fuel absorption.
These and other objectives of the present invention will become apparent from the detailed description of preferred embodiments which follow.